1. Field of the Invention
The present invention relates to a power transmission arrangement in a working vehicle with a working unit such as a cultivating unit and mower unit attached thereto, and a transmission for the working vehicle.
2. Related Art
In a vehicle equipped with a working unit such as a bucket, cultivating unit and mower unit on the front side, rear side and/or below the lengthwise center of a chassis, driving power from a driving power source must be divided into a running power transmission path and a driving power transmission path for working unit so as to be transmitted to driving wheels and the working unit. This poses a problem of increasing a size of the transmission in the vehicle.
For example, Japanese Patent Application Publication No. Hei-01-17883 and Utility Model Application Publication No. Hei-01-37298 disclose arrangements, which are applicable to the vehicle of the above type, for downsizing the size of the transmission.
The transmission disclosed in each of the above-cited publications has an input shaft for the working unit (PTO input shaft) and a running power input shaft, which are respectively aligned in vertical and parallel relationship with each other, and a transmission case in which the power transmission path for working unit and the running power transmission path are arranged respectively closer to upper and lower sides thereof with occupation of spaces as much compact as possible in an attempt to reduce the size of the transmission.
Meanwhile, for the vehicle equipped with a working unit as mentioned above, a hydraulic power unit for operating the working unit must be provided in some cases, in addition to a power-take-off arrangement for taking off driving power for the working unit. As such a hydraulic power unit, it can be cited a hydraulic lift unit for lifting a cultivating unit mounted on the rear side of the chassis.
As described above, in each of the above-cited publications, although the downsizing of the transmission may be achieved by arranging the running power transmission path and the power transmission path for working unit within the transmission case respectively closer to the upper and lower sides thereof with occupation of spaces as much compact as possible, such downsizing was not considered for the transmission of the vehicle provided with the aforesaid hydraulic power unit.
Specifically, in a vehicle disclosed in each of the cited publications, a hydraulic power unit for reciprocating a cultivating unit or any other working unit is disposed on a top surface of the transmission, while a hydraulic pump for feeding pressurized fluid to the hydraulic power unit is supported on a rear wall of the transmission case.
More specifically, in the transmission described in each publication, a clutch shaft and an intermediate shaft, which constitute a part of the power transmission path for working unit (PTO system), extend below and on the opposite lateral sides of a PTO input shaft, so that an upper space of the transmission case is occupied by this PTO power transmission path. Accordingly, in this conventional transmission, it is not possible to secure within the transmission case closer to the upper side a space for accommodating the hydraulic pump for feeding pressurized fluid to the hydraulic power unit, a driving power transmission mechanism for the hydraulic pump, etc. For these reasons, the conventional transmission has the hydraulic pump supported on the rear wall of the transmission case and a rear end of the PTO input shaft extending through the rear wall of the transmission case, through which the hydraulic pump is driven.
Thus, for the vehicle equipped with the hydraulic pump, the hydraulic pump of the conventional transmission extending rearwards through the transmission case poses a difficulty in shortening the length of the transmission with the hydraulic pump.
Also, according to the above arrangement, working fluid reserved in the transmission case for the hydraulic power unit is once transmitted around the rear side of the transmission case and then to the upper side of the transmission case. Accordingly, a hydraulic fluid circulation path to the hydraulic power unit must be elongated, which necessitates application of an excessive load to the hydraulic pump.
As another disadvantage involved in the vehicle described in each cited publication, since the hydraulic power unit is disposed on the top surface of the transmission case, a higher position must be prepared for mounting of the hydraulic power unit. This arrangement poses a problem of increasing an vehicle height. Since a driving seat is above the hydraulic power unit in a general arrangement, this invites a difficulty for a driver to get on and off the seat.
As described above, the power transmission path for working unit of the conventional transmission is entirely located in the upper space of the transmission case. On the other hand, a mid-PTO shaft for driving a mid-mount more or the like is located in the lower space of the transmission case. Accordingly, a power transmission mechanism between the PTO input shaft and the mid-PTO shaft in the conventional transmission must be formed throughout the entire region of the transmission case along the vertical direction. This poses a problem of necessitating a complicated structure for the transmission mechanism.
The present invention was conceived in light of those conventional techniques. It is an object of the present invention to provide a transmission with the power transmission path for working unit and the running power transmission path, which is capable of achieving downsizing of the transmission case, as well as effectively securing a space for accommodating parts for the hydraulic lift unit or the like within the transmission case.
It is another object of the present invention to provide a power transmission arrangement in a vehicle provided with a working unit operable by a hydraulic power unit, which is capable of shortening a hydraulic fluid distribution path to the hydraulic power unit.
It is still another object of the present invention to provide a power transmission arrangement in a vehicle provided with a working unit operable by a hydraulic power unit, which is capable of stably supporting a cylinder tube of the hydraulic power unit at a lower position.